Salatul tasbih in congregation

It is Makruh to hold congregation for nafl prayers. Therefore, as Salatul Tasbih is a nafl prayer it will be Makruh to perform it in congregation.

However, if a group of people gather (4 including the Imam) and do the Salah in congregation it will be permissible according to the view of Imam Muhammad. (Raddul Muhtar p.500 v.2 & Badaaius Sanaii p.290 v.1)